HP Surestore Disk Array 12h - And FC60, Advanced User'S Manual, Page: 76 / 466

76
Array Design Considerations
another, two or one disk enclosures, respectively, can be added by using split-bus mode.
However, if you are adding up to four, five, or six enclosure, the enclosures configuration
will need to be switched from split-bus to full-bus (refer to “Disk Enclosure Bus
Configuration” section, earlier in this chapter, for additional information).
Note
Typically adding only one enclosure does not provide any options for creating
LUNs. It is best to expand the array with at least a minimum of two disk
enclosures at a time. Two additional drives could then be configured as RAID 1
or 0/1.
Installing a five disk enclosure array limits expansion to six disk enclosures.
Adding one additional enclosure does not provide any versatility for creating
LUNs (unless all data is removed and the LUNs are rebuilt).
If the initial installation uses split-bus disk enclosure (split-bus accepts three disk
enclosures maximum) and expansion requires adding four or more enclosures, the existing
disk enclosures will need to be reconfigured for full-bus mode and the additional number
of enclosures installed into the rack and required number of full-bus enclosures. This
expansion requires disk enclosures be recabled using full bus enclosures. As in all cases of
adding disk enclosures to the array, the system has to be shut down for the expansion.
Determine the RAID level and how the LUNs will be created for the expansion
If the initial installation consisted of one or more full-bus configured disk enclosures, then
additional full-bus configured disk enclosures can be added to the array. The system should
be shut down for the addition of the enclosures. Determine the RAID level and how the
LUNs will be created for the additional storage.
To scale up sequential performance, first make sure that the configuration includes both
controllers modules. Maximum sequential transfer performance will be reached with
approximately 20 disk modules simultaneously transferring data. To achieve additional
sequential transfer performance, you will need to add a second disk array and more disk
modules.
To increase I/Os per second performance, add disk modules. Transaction performance is
directly related to the number of disk modules installed in the disk array.